Fix a couple typos in api specification

appapi.yaml

@@ -39,7 +39,7 @@ paths:
         '200':
           description: Success
           content:
-            applicaion/json:
+            application/json:
               schema:
                 type: object
                 description: As the endpoint is public, just try it out.
@@ -251,7 +251,7 @@ paths:
                   - field
                 properties:
                   field:
-                    description: The field which failed, eiter 'username' or 'email'. If both, the email address and the username, are already used, the field will be 'username'. 
+                    description: The field which failed, either 'username' or 'email'. If both, the email address and the username, are already used, the field will be 'username'. 
                     type: string
         '500':
           description: The server cannot deliver due to an internal error.
@@ -680,10 +680,10 @@ paths:
   '/duel/report':
     post:
       summary: Report a mistake in a question.
-      description: Endpoint to report a mistake in a question, its answers or its explaination.
+      description: Endpoint to report a mistake in a question, its answers or its explanation.
       parameters:
         - name: question
-          description: ID of the falty question.
+          description: ID of the faulty question.
           in: query
           required: true
           schema:
@@ -1052,7 +1052,7 @@ components:
     error:
       description: General error.
       type: string
-      default: An unexpected error occured
+      default: An unexpected error occurred
     login:
       type: object
       required:
@@ -1088,7 +1088,7 @@ components:
           format: int32
     userinfo:
       description: >-
-        Information on a user that is publicly availabe to other users.
+        Information on a user that is publicly available to other users.
       type: object
       required:
         - username